(a) Field
The following description relates to a method of preparing a counter electrode for a dye-sensitized solar cell (DSSC) using a laser, and more particularly, to a low temperature sintering method of a catalyst layer of the counter electrode using a laser for preparing a counter electrode of a flexible DSSC.
(b) Background
In the DSSCs, the counter electrode may reduce redox species which were used as the media for recycling dyes after an electron injection. The counter electrode should have a sheet resistance as small as possible and a high reduction reaction speed to the redox electrolytes. For this, platinized transparent counter electrodes and counter electrodes including carbons, conductive polymers, and the like, have largely been used. The electrodes including polymer/carbon or polymer/platinum together are largely being used as the counter electrodes of the flexible DSSC. Particularly, a platinum-loaded conductive glass substrate is most widely used as the counter electrode of the DSSC.
Thermal sintering is the method that is most widely used for sintering platinum which is used as a catalyst for a redox reaction of electrolytes. For example, chloroplatinic acid (H2PtCl6), a platinum precursor, may be dissolved in a volatile solvent such as propanol and coated on a glass substrate by a spin-coating or dropping method, wherein the glass substrate is coated with a fluorine-doped tin oxide (FTO), and the substrate is sintered by heat-treating the same at 400° C. for approximately 20 minutes.
However, the thermal sintering has a disadvantage of being time-consuming. Furthermore, when a plastic substrate is used for the counter electrode, the thermal sintering method cannot be carried out because the plastic substrate is damaged at the high temperature. Therefore, in the case of flexible DSSC, counter electrodes have been prepared by a sputtering method or an electrochemical method that deposits platinum on a plastic substrate of ITO-PEN or conductive polymer at room temperature. Such methods have an advantage of decreasing the damage of the plastics used as the electrode substrate by using a low temperature process. However, these methods have a disadvantage of requiring many processes.